This invention relates to power actuators and more particularly to a power actuator for lifting a pivotal lift gate closing an access opening in a motor vehicle body.
Motor vehicles of the hatchback and van configuration typically include an access opening at the rear of the vehicle body and a lift gate selectively opening and closing the access opening. The lift gate is typically manually operated and specifically requires manual effort to move the gate between open and closed positions. Various attempts have been made to provide power actuation for the lift gate but none of the prior art power actuation systems have realized any significant degree of commercial success since they have either been unduly complicated, relatively expensive, or maintenance prone.
This invention relates to a power actuator for lifting a pivotal lift gate closing an access opening in a motor vehicle body.
According to the invention, the power actuator comprises a motor assembly adapted to be secured to the motor vehicle body proximate the access opening; a rotary flexible cable having a driven end driven by the motor assembly and a driving end; and an extensible strut including an upper mounting structure proximate an upper end of the strut for pivotally mounting the upper end of the strut to the lift gate, a lower mounting structure proximate a lower end of the strut for pivotally mounting the lower end of the strut to the motor vehicle body proximate the access opening, means proximate the lower end of the strut for receiving the driving end of the cable, and means for extending the strut in response to rotation of the cable by the motor assembly whereby to raise the gate in response to actuation of the motor assembly. This arrangement provides a simple, effective, and relatively inexpensive system for raising and lowering the gate.
According to a further feature of the invention, the extensible strut includes a lower tubular housing member, a lead screw mounted for rotation in the tubular housing member and including a lower head portion journaled in a lower portion of the tubular housing member and an upper threaded shank portion, and a tubular extender rod telescopically and slidably positioned in the tubular housing member in concentric surrounding relation to the lead screw shaft portion and including a nut structure at a lower end thereof threadably receiving the lead screw shaft portion; the lower mounting structure is provided proximate the lower portion of the tubular housing member; and the upper mounting structure is provided proximate an upper end of the tubular extender rod. This arrangement provides a simple and compact strut construction for effecting the raising and lowering of the gate.
According to a further feature of the invention, the lower portion of the tubular housing member defines a cavity; the head portion of the lead screw is journaled in the cavity; the receiving means includes an aperture in a lower end of the tubular housing member communicating with the cavity; the driving end of the cable passes through the aperture and drivingly engages the head portion of the lead screw; and the extending means is constituted by the threaded engagement of the lead screw shaft portion with the nut structure. This specific construction provides an effective arrangement for extending the strut in response to rotation of the cable.
According to a further feature of the invention, the actuator further includes bearing means positioned in the cavity and journaling the lead screw head portion. This arrangement facilitates the smooth rotation of the lead screw within the housing member.
According to a further feature of the invention, the motor assembly includes an electric motor and a speed reducer driven by the motor. This arrangement allows the use of readily available motor and speed reducer assemblies to provide the motor power for the actuator.
According to a further feature of the invention, the threads of the lead screw shaft portion and the nut structure have a pitch angle of at least 20xc2x0. This specific arrangement enables the lead screw to spin relatively freely in the nut structure as the gate is raised and lowered manually so as to offer minimal resistance to the manual raising and lowering of the gate.
According to a further feature of the invention, the motor assembly includes a clutch downstream of the motor effective to drive the cable from the motor but ineffective to drive the motor from the cable. This arrangement avoids back driving of the motor in response to manual operation of the lift gate.
The invention also provides an improved actuator for providing relative movement between first and second structures. The improved actuator comprises a lower tubular housing; a lead screw having a lower head portion journaled in a lower portion of the tubular housing and a threaded shaft portion extending upwardly from the head portion within the tubular housing; a tubular extender rod positioned slidably and telescopically within the tubular housing in concentric surrounding relation to the shaft portion of the lead screw and including a nut structure proximate a lower end thereof threadably engaging the shaft portion of the lead screw; a mounting structure on the tubular housing for mounting the tubular housing on the first structure; a mounting structure on the tubular extender rod for mounting the tubular extender rod on the second structure; and a drive mechanism engaging the head portion of the lead screw and operative to rotate the lead screw relative to the tubular housing whereby to move the tubular extender rod axially relative to the tubular housing and provide relative movement between the first and second structures. This actuator construction provides a simple, effective, and inexpensive actuator for providing movement between two structures.
Other objects, advantages and applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.